Robert made a tunnel using some identical cubes (fig.1). When he got bored, he rearranged the tunnel into a complete pyramid (fig.2). How many cubes from the original tunnel did he not use for the pyramid?
A. 34 B. 29 C. 22 D. 18 E. 15
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its 18
ReplyDeleteThe center layer is 18 blocks. But the question is how many blocks were NOT used from the original design...
ReplyDeleteim just doing this fast and mentally
ReplyDelete72 - 41? ... =31 ?
# of blocks used for tunnel : 20+12+12+20 = 64
ReplyDelete# of blocks used for pyramid ; 25+9+9+3 = 46
Diff = 18 (D)